Hexachlorocyclopentenone preparation



Patented Sept. 1, 1953 HEXACHLOROCYCLOPENTENONE PREPARATION Earl T.McBee and Jack S. Newcomer, West Lafayette, Ind., assignors to PurdueResearch Foundation, West Lafayette, Ind., a corporation of Indiana NoDrawing. Application October 1, 1948, Serial No. 52,405

3 Claims.

The present invention relates to a method of treatingoctachlorocyclopentene, and is more particularly concerned with a methodof forming hexachlorocyclopentenone directly from octachlorocyclopenteneby treatment thereof with Sulfuric acid. This application is acontinuation-in-part of our application Serial 757,949, filed June 28,1947, which issued as Patent 2,493,009.

Prior methods for the preparation of hexachlorocyclopentenone (2,3,4,4,5,6-hexachloro-2- cyclopentene-l-one) involve the use of a sevenstepprocedure. The last four steps involved are i) chlorination of3,5-dihydroxybenzoic acid to a pentachlorodioxobenzoic acid, 2) furtherchlorination under different conditions to a hexachlorocyclohexenedione,3) treatment with weak base to form a hydroxycyclopentenoic acid, andf1) oxidation with nitric acid. It may readily be seen that the cost ofhexachlorocyclopentenone prepared by such a method is exorbitant.

It is an object of this invention, therefore, to provide a practicalsingle-step process for the preparation of hexachlorocyclopentenone. Itis a further object of the present invention to producehexachloroeyclopentenone directly from octachlorocyclopentene in asingle step. Another object of the invention is the provision of a novelprocess for the treatment of octachlorocyclopentene with sulfuric acid.Other objects will become apparent hereinafter.

The compound prepared by the method of the present invention is animportant intermediate in the preparation of more complex organicmolecules, such as perchloroindone, which may be subsequently convertedto tetrachlorophthalic anhydride, a valuable constituent in thepreparation of resins of the glyceryl phthalate type.

The process of the present invention includes the reaction of sulfuricacid with octachlorocyclopentene. The result of our new process Was notto be expected, since a chlorocarbon ketone is not obtained by thereaction of hexachlorocyclopentadiene and sulfuric acid. The reactioncan be performed in any suitable manner, such as by adding the sulfuricacid to the octachlorocyclopentene, with the reverse procedure alsobeing satisfactory. Any suitable temperature may be used, and attainmentof a satisfactory temperature range is evidenced by evolution ofhydrogen chloride. Temperatures between about 60 degrees and about 150degrees centigrade are suitable, with the optimum temperature beingbetween about 95 degrees and 110 degrees centigrade, although othersomewhat higher or lower temperatures may be used if desired. The timeallowed for the reaction is dependent upon a number of factors, such asconcentration of the reactants employed, amount of reactants present,temperature, method of agitation, et cetera. However, a period of aboutseven hours or less is usually satisfactory, or when the sulfuric acidlayer of the reaction mixture has turned to a dark. brownish-black.Agitation is preferably employed to ensure efficient contact of thereactants which will reduce the time required for the reaction. Thereactants are employed in at least equimolar quantities, and sulfuricacid is ordinarily employed in molar excess, how much excess beingdependent upon the quantity of reactants used, temperature, et cetera.The use of concentrated sulfuric acid is a preferred embodiment of thepresent invention, that is, sulfuric acid of a concentration of over 50percent and preferably above about percent. The hexachlorocyclopentenonemay be separated from the reaction mixture, e. g., by decanting orquenching on ice, and purified in any conventional manner, such as byrecrystallization, which will be apparent to one skilled in the art.

The following examples are given to illustrate the practice of thepresent invention but are not to be construed as limiting.

Example 1 A mixture of octachlorocyclopentene (150 grams, 0.44 mole) andconcentrated sulfuric acid (900 grams, 8.5 moles) was placed in athreeneck flask equipped with a motor-driven stirrer, thermometer, andreflux condenser. The evolution of hydrogen chloride became appreciableat about degrees centigrade. The temperature was maintained at 100-110degrees centigrade, during which time the reaction mixture darkened.After seven hours, it appeared as if little or no reduction of the upperorganic layer had resulted. The reaction product was cooled and pouredonto ice. The resulting liquid product was recrystallized three timesfrom petroleum ether to give 87 grams of a liquid (M. P. 22-24 degreescentigrade, 73.0 percent chlorine). Hexachloro-2-cyclopentene-l-onemelts at 28 degrees centigrade and contains 73.6 percent chlorine.

Example 2 A mixture of octachlorocyclopentene (1932 grams, 5.34 moles)and concentrated sulfuric acid (2600 grams, 25.5 moles) was placed in athree-neck flask equipped with a thermometer, stirrer, and aircondenser. The mixture was heated for seven hours at degrees centigrade.

After cooling the reaction mixture to room temperature, the upper,light-yellow layer was separated from the lower, black sulfuric acidlayer. After washing with water, the yellow oil weighed 1260 grams. Theoil was crystallized from an equal volume of n-pentane to give a highyield of hexachloro-2-cyclopentene-1-one.

Various modifications may be made in the present invention withoutdeparting from the spirit or scope thereof, and it is to be understoodthat we limit ourselves only as defined in the appended claims.

We claim:

1. A process for the production of hexachlorocyclopentenone whichcomprises heating together octachlorocyclopentene and more than anequimolecular proportion of aqueous sulfuric acid having a concentrationin excess of approximately 50 percent by weight of H2804, andsubsequently recovering the hexachlorocyclopentenone from the reactionmixture.

2. A process for the production of hexachloro- .cyclopentenone whichcomprises heating together octachlorocyclopentene and more than anequimolecular proportion of aqueous sulfuric acid having a concentrationin excess of approximately 70 percent by weight of H2804, at atemperature between approximately 60 and approximately 150 degreescentigrade, and subsequently recovering the hexachlorocyclopentenonefrom the reaction mixture.

EARL T. MCBEE. JACK S. NEWCOMER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,849,844 Lloyd et a1 May 15, 1932 2,481,157 Schmerling Sept.6, 1949 FOREIGN PATENTS Number Country Date 570,668 Great Britain July17, 1945 OTHER REFERENCES McCombie et al., J. Chem. 300., vol. 103, pp.1995-2006 (1913).

Prins, Rec. trav. chim. des Pays Bas, vol. 51, pp. 1065- (1932).

Prill, J. A. C. S., 69, 63 (1947).

Prins, Rec. des Trav. Chim. Des Pays Bas 65, 445 to 467.

1. A PROCESS FOR THE PRODUCTION OF HEXACHLOROCYCLOPENTENONE WHICHCOMPRISES HEATING TOGETHER OCTACHLOROCYCLOPENTENE AND MORE THAN ANEQUIMOLECULAR PROPORTION OF AQUEOUS SULFURIC ACID HAVING A CONCENTRATIONIN EXCESS OF APPROXIMATELY 50 PERCENT BY WEIGHT OF H2SO4, ANDSUBSEQUENTLY RECOVERING THE HEXACHLOROCYCLOPENTENONE FROM THE REACTIONMIXTURE.